In an image-capturing apparatus, such as a video recorder with a camera (hereinafter, referred to as camcorder) and a digital still camera, image blur is corrected, for example, by mechanically adjusting the optical system. Such a method is typified by an “antivibration lens-shifting method” where a shiftable lens is moved according to the amount of image blur, and a “vari-angle prism (VAP) method” where a vari-angle prism is tilted according to the amount of image blur.
In such a method for correcting image blur, image-blur signals in the image-capturing apparatus are detected, for example, by an angular-velocity sensor. Then, computations, such as integration, are performed on the detected signals to determine the target value for image-blur correction. Correction of the optical system is thus controlled such that image blur is corrected based on this target value.
On the other hand, image-capturing apparatuses incorporate an autofocus function to automatically focus on the subject to be captured. In the autofocus function, image contrast is detected based on the light from the subject. Optical lenses are then adjusted to maximize the contrast. In such an autofocus function, focus control is difficult to perform under low-light conditions or when the subject itself has a low contrast. Therefore, a fill-light projector, including a light, which is installed in the image-capturing apparatus projects a projection pattern onto the subject. The autofocus function performs control to maximize the contrast of the projection pattern projected onto the subject.
However, when the image-blur correcting function described above and the autofocus function at the time of fill-light projection are simultaneously used, the image-blur correcting function performs control to prevent image blur with respect to the subject, thereby causing image blur in the projection pattern, which is projected by the fill-light projector installed in the image-capturing apparatus, with respect to the optical system in the image-capturing apparatus. This image blur may cause the fill-light projection pattern to move into and out of a detection frame defining a contrast detection range for autofocus, or may cause the projection pattern to deviate from the detection frame.
Moreover, in an image-capturing apparatus having a zoom function, the distance between portions of the fill-light projection pattern is widened at high zoom factors and the projection pattern may be completely off the detection frame, even though the projection pattern falls within the detection frame at low zoom factors.
To prevent such cases, a step is provided, in the manufacturing process, for adjusting the fill-light emitting position such that the fill-light projection pattern falls within the detection frame at the highest zoom factor. However, when image blur is corrected by the image-blur correcting function, the fill-light projection pattern simultaneously swings and may be completely off the detection frame.
Possible measures include increasing the pattern density of the projection pattern, making the density of the projection pattern variable according to the zoom factor, and moving the projection pattern in the same direction as that of the image-blur correction. However, in the case where the fill-light projector includes a light source, such as laser light, having a high energy density that involves control of intensity and pattern density, increasing the pattern density of the projection pattern or making the density of the projection pattern variable according to the zoom factor is difficult because of safety concerns. In addition, the image-capturing apparatus has structural constraints in moving the projection pattern in the same direction as that of the image-blur correction and may require additional apparatuses.
A method for solving these problems is to stop the image-blur correcting function during the projection of fill light. A problem in this method is that no image-blur correction is performed during the projection of fill light. Moreover, stopping the image-blur correcting function is accompanied by noise or vibration in the image-capturing apparatus. Even though the image-blur correcting function is restarted after the completion of the fill-light projection such that the effect of the image-blur correction at the time of exposure of images can be obtained, there is a delay until the effect of the correction becomes evident. However, control for preventing such delay causes the occurrence of noise or vibration.
As described above, the accuracy of the autofocus function is degraded when the image-blur correcting function and the autofocus function at the time of fill-light projection are simultaneously used.
Moreover, since autofocus does not effectively work, at the time of fill-light projection, when fill light is projected onto a subject that is not suitable for the fill light (that is, for example, a subject absorbing the fill light, allowing the fill light to pass through, or placed in an area, such as the end of the screen, where no fill light reaches), the autofocus may be performed based on information on images obtained by light other than the projection pattern. If the image-blur correcting function is stopped in this case, the accuracy of the autofocus function performed based on information on images obtained by light other than the projecting pattern, through the effective use of the image-blur correcting function, and the accuracy of other functions, such as exposure control and color control, are degraded.